1. Field of the Invention
The present invention relates to a method of fabricating a dielectric layer, and more particularly, to a surface treatment process applicable to a dielectric layer of a shallow trench isolation (STI).
2. Description of the Prior Art
In the design of semiconductor devices, each metal-oxide-semiconductor (MOS) transistor component must be well isolated to prevent interference and short-circuiting. In general, localized oxidation isolation (LOCOS) or shallow trench isolation (STI) methods are used to isolate and protect MOS transistors. In the LOCOS process, a field oxide layer occupies a very large area on the semiconductor wafer, and a bird's beak is generated. Therefore, the STI having the advantages of small isolation line width, explicit division of active regions, uniform depth of isolation regions, scalable size and excellent planar structure of isolation regions has become a preferred ideal isolation technology at present.
The common processes of forming a STI are described as follows. First, recesses are formed in the semiconductor substrate between MOS transistors. Then, the recess is filled with insulating material, and the insulating material is further planarized to be an insulating region used for isolation. With a trend towards scaling down the size of MOS transistors for achieving high integration rates, when a chemical vapor deposition (CVD) process is used to deposit a dielectric layer to fill the recess, the high aspect ratio of the recess may cause overhang at the top corner of the recess, and voids may be found in the formed STI.
During the conventional manufacturing processes of the semiconductor device, the etching process and the cleaning process, such as an etching process for removing a cap layer and a hard mask layer on each transistor, an etching process for forming spacers, a pre-cleaning process performed after the etching process for forming the spacers, a cleaning process performed after forming the source/drain electrode in the active region, a pre-cleaning process performed before forming the silicide layers, and an etching process for removing metal layers without reacting, are performed several times. During the etching processes and the cleaning processes, the exposed STI is damaged by the etching processes and the cleaning processes, thereby forming breaks on the surface of the STI, or spaces in the interface between the STI and the substrate.
Consequently, how to improve the STI process in order to prevent the formation of the illustrated defects and to avoid the current leakage is an important issue in this field.